{ 1 } - there are two kinds: simple and complex.
{ 2 } - there are four kinds: declarative, interrogatory, imperative, and exclamatory.
{ 3 } - we can divide up sentences in various ways -- so how many "kinds" there are depends on our purposes.

The question about "how many kinds" doesn't make clear sense without a further context.

When discussing grammar, we may be interested in dividing sentences into declarative, interrogatory, imperative, and exclamatory groups. In other contexts, we might be interested in other distinctions -- for example, short vs. long sentences, true vs. false sentences, or literal vs. metaphorical sentences.